1. Field of the Invention
This invention relates to a lubricating system for bearings and in particular to a system for supplying lubricant across the width of a belt conveyor idler assembly to bearings that are at varying distances from a pressure source supplying lubricant to the system.
2. Description of the Prior Art
Belt conveyor systems typically carry raw and processed materials such as mined ore, crushed rock, coal, phosphated fertilizers and other such abrasive, corrosive, powdered material in a process environment which requires reliable, continuous service and operation. Bearings, which support the loads traveling on these conveyors, are particularily susceptible to failure in view of the offensive environment in which they perform and the speeds and loads involved. Unless supplied continually with an adequate lubricant, excessive wear results and the ultimate failure of the bearing is assured. Process industry personnel typically prefer to lubricate conveyor bearings from one side of the conveyor only, with a view to saving time and cost, and because access to bearings on both sides of the conveyor is often unpredictable and unavailable. Even if access were available from both sides, intermediate bearings are not readily within view or reach of the lubrication attendant. For these reasons idler bearing systems have been designed with the remote lubrication feature as a requirement.
Clearance seals, generally of the labryrinth type, are commonly in use at the outer ends of the individual shaft segments because of their satisfactory performance characteristics relating to efficiency, as measured by power absorbed in the form of frictional losses, and their ability to seal the bearings against inward migration of abrasive, corrosive contaminants. As a further precaution against bearing failure from such foreign matter, the lubrication system should provide capability for flow outward from the inner side of the bearing in sufficient quantities and rate of flow as to flush out the offensive material in the outward wash of lubricant.
U.S. Pat. Nos. 3,797,609 and 4,051,921 apply to the subject matter of this invention. The former is related to a method for supplying lubricant to the support bearings of a belt conveyor idler by means of tubular members which connect a spindle to the bearings. The length of the tubes and their diameters are chosen to establish a pressure drop in the tube between the spindle and the bearing so that lubricant will flow to each bearing regardless of its distance from the pressure source. As the distance from the pressure and lubricant source increases, as it necessarily must for each bearing position across the conveyor width, the pressures drop in the spindle supply passage will accumulate to such a degree that there will be substantially less pressure in the passage at the most distant bearing than exists at the bearings closest to the source. This produces a condition which can result in insufficient and inadequate lubricant supply to the most distant bearings, the ultimate failure of the bearing, and substantial down-time for replacement.
The second patent cited discloses an attempt to increase the amount of lubricant flowing to the more distant bearings by means of a constriction placed over or adjacent the orifice created by radial holes leading from the major supply passage to the bearing. This approach required the placement of minuscule plugs in the bore of the shaft at locations precisely positioned to constrict flow from the radial hole. It caused undue delay in the fabrication process since shop operators who handle equipment of the size and bulk of conveyor components are unaccustomed to tedious and exacting work of this sort.